问题
I'm planning to switch an app from the old OAuth flow with the SFSafariViewController to the new flow with iOS 11's SFAuthenticationSession. Logging in isn't an issue, the transfer to the new API took me a few minutes to implement. However logging out has me baffled.
How?
I can't find any mentioning of wanting to offer the option of logging out anywhere in the docs. Using the old SFSafariViewController to invalidate the cookies? Nope, they're not shared anymore with SFAuthenticationSession. As soon as I restart the authentication session the user get's logged in automatically and there's no way out. So how to enable logging out? Or am I simply overlooking something completely obvious?
Update: I found a "way that works" in a technical sense, but it's bonkers for the user: Open a new SFAuthenticationSession on the logout page that clears the cookie. But that means when logging out the alert view asks the user again whether he'd like to log in via the service. If yes is selected ("logging in"), the cookie clearing logout page is opened, the user has to manually dismiss the view, which can be caught by the completion handler and we know we can open the login view again.. displaying the login prompt to log out? I really don't like this solution.
Any ideas? Am I still overlooking a completely obvious solution?
Update 2: As no one has any clue about this issue so far, this is probably not an easy one. I have filed a suggestion with Apple via their report tool to either clarify how to handle this or build it into the API if not available. Will post if I get an answer.
Update 3: After pondering the issue a bit more we found another possible (although also unattractive) solution if you can influence the login page of the OAuth provider: make cookies very short lived. Then the login page can be opened without automatic log in. However this kills the whole purpose of sharing login sessions between apps.. and you need to be able to influence the login page.
Update 4: Since iOS 12 SFAuthenticationSession is deprecated and got replaced by ASWebAuthenticationSession. However ASWebAuthenticationSession does not change anything in regard to logging out. It's still not possible. Same issue as before.
回答1:
One of the “best” solutions I have come across is to open a logout page in system Safari (not an SFSafariViewController). Because ASWebAuthenticationSession shares cookies reliably with Safari, the expired/deleted cookie then also affects the app.
See this GitHub page for more details.
回答2:
It depends on which cookie stores your login info;
If it is a session cookie, then it is not shared with Safari as per https://developer.apple.com/documentation/authenticationservices/aswebauthenticationsession
So, simply clear your local session, and the cookies will be cleared on the next app launch.
If not, and the cookie persists, then like Martin said above, you should open Safari (not SFSafariViewController) with your logout URL, then redirect back to your app.
Please let me know if you need more info. I have tested extensively with all 3 ways of authentication (ASWebAuthenticationSession, Safari, and SFSafariViewController).
来源：https://stackoverflow.com/questions/47207914/sfauthenticationsession-aswebauthenticationsession-and-logging-out